Low emissivity, or low-e, panels are often formed by depositing a reflective layer (e.g., silver), along with various other layers, onto a transparent (e.g., glass) substrate. The various layers typically include various dielectric and metal oxide layers, such as silicon nitride, tin oxide, and zinc oxide, to provide a barrier between the stack and both the substrate and the environment, as well as to act as optical fillers and function as anti-reflective coating layers to improve the optical characteristics of the panel.
When used in, for example, windows, and depending on the particular environment (i.e., climate), it may be desirable for the low-e panels to allow solar radiation to pass through the window in one direction and block heat from passing through in the opposite direction. For example, in relatively cold climates, it may be desirable to allow solar radiation to pass through the panel from the exterior to the interior of a building, but prevent (or minimize) heat on the interior from escaping back through the panel to the exterior.
Such operation may facilitate maintaining a suitable temperature on the interior of the building and reduce heating costs. Such panels (or windows) are often referred to as “high solar gain” panels. In order to maximize the performance of these panels, it is desirable to increase the solar gain (sometimes referred to as “g-value”) as much as possible, while maintaining suitable optical characteristics.